I'm running Hudson 1.321 and some of my projects that poll SVN keep being
rebuilt even though the build pages state "No change".

The most I've seen is seven rebuilds even though nothing is reported as changed.

Here is an example from today:

Build #196 (Aug 25, 2009 2:03:07 PM)
Revisions
...
No changes.
A SCM change trigger started this job

Build #197 (Aug 25, 2009 2:15:23 PM)
Revisions
...
No changes.
A SCM change trigger started this job

Build #198 (Aug 25, 2009 2:31:58 PM)
Revisions
...
No changes.
A SCM change trigger started this job

And it continues like this until build 202, which is the final build until the
next real SCM change occurred.

I poll SVN every five minutes with a quiet period of 120 seconds. All jobs run
on the master, which is a Windows machine.

I've searched old reports and have found several that resulted in similar
behavior, but all of the were closed.